The present invention relates to a weft reservoir for fluid jet looms, and more particularly relates to an improvement in the construction and operation of a weft reservoir for fluid jet looms wherein the weft is wound about a reservoir drum including conical and cylindrical sections through relative rotation between a yarn guide and the reservoir drum, reserved thereon and delivered therefrom for weft insertion under pin control.
In the following description, the side of the arrangement closer to the supply source of the weft is referred to in general as "the upstream side" whereas the side of the arrangement closer to the main jet nozzle for insertion of the weft is referred to in general as "the downstream side".
Weft reservation under pin control on a weft reservoir is roughly classified into two major types. In the first type of weft reservation, coils of weft for different cycles of weft insertion are separately reserved by cooperation of two or more control pins and, as a result of inter-pin assignment, are moved downstream on the reservoir drum. At the moment of weft insertion, coils of weft for that cycle of weft insertion are released by hold of the most downstream side control pin for delivery from the reservoir drum. In the case of this type, coils of weft for different cycles of weft insertion can be reserved in a fairly separated state and delivered quite independently of each other. But this type of weft reservation requires use of a relatively complicated mechanism to assure exactly phased movements of the control pins for proper inter-pin assignment of the weft and opportune release of weft for delivery.
In the second type of weft reservation, a sufficiently large number of coils of weft are reserved on the reservoir drum without any clear separation with use of a single control pin in engagement with the most downstream coil of weft. At the moment of weft insertion, the control pin is retained out of engagement with the weft, which is then subjected to delivery from the reservoir drum. When coils of weft for one cycle of weft insertion have been delivered from the reservoir drum, the control pin is brought into engagement with the most downstream coil of weft remaining on the reservoir drum. This type of weft reservation avoids the necessity for separate reservation of weft by two or more control pins. In addition, this type of weft reservation is very advantageous from the viewpoint of stable reservation of weft on the reservoir drum. The larger the number of coils of weft wound on the reservoir drum, the smaller the possibility of undesirable, accidental, slip-out of weft from the reservoir drum during the delivery of weft for weft insertion. Apparently such slip-out of weft lends to superfluous delivery of weft at that cycle of weft insertion and, further, to insufficient delivery of weft for the next cycle of weft insertion. Such slip-out of weft also tends to cause undesirable slippage of the weft on the reservoir drum in particular at the starting period of winding, which disables the reservation of the correct number of coils of weft for the next cycle of weft insertion. Despite such advantages, it is prerequisite to this type of weft reservation to provide a special expedient such as a photo-electric system to detect the number of coils of weft to be unwound from the reservoir drum during the delivery for weft insertion. In addition, the result of such detection has to be properly processed in order to incite a corresponding mechanical movement of the control pin. This also requires use of another complicated mechanism.
It is therefore strongly desirable to practice the above-described second type of weft reservation without complicating the mechanism of the weft reservoir involved.
Even when this requirement is satisfied and a control pin is very timely registered at its operative position for engagement with weft on the cylindrical section of a weft reservoir, the conventional construction of the weft reservoir, i.e. the uniform diameter of the cylindrical section for reservation of weft, cannot assure perfect prevention of the above-described accidental slip-out of weft at delivery.
It is then also required to provide a reliable expedient to prevent accidental slip-out of weft at delivery.
Aside from these requirements for a simple mechanism and stable the weft delivery without accidental slip-out of weft at delivery, care should be directed to the fact that operation of the control pin, more specifically maintaining control pin at its stand-by position, is closely related to the associated running of the loom, and that, as long as the main jet nozzle is in operation, coils of weft are freely delivered from the reservoir drum when the control pin is maintained at its stand-by position out of engagement with the weft under delivery. As explained already, the control pin is brought back to its operative position in engagement with the weft at a moment when coils of weft for one cycle of weft insertion have been delivered from the reservoir coil as long as normal loom operation continues.
Trouble starts when the loom stops running due to some accident such as yarn breakage in particular at the very moment of weft insertion. Coils of weft on the reservoir drum are delivered therefrom due to traction of the main jet loom in operation since the control pin has already been moved to the stand-by position out of engagement with the weft under delivery. Delivery of weft goes on but the control pin isn't brought back to the operative position since its operation is closely related to the running of the loom which has already stopped. As a consequence, more coils of weft are delivered than necessary for one cycle of weft insertion, which apparently causes insufficient weft delivery for the next cycle of weft insertion.
It is therefore strongly required that excessive delivery of weft should be prevented even when the loom stops its normal running even at the very moment of weft insertion.